THE INHIBITION OF IRON CORROSION IN ACID-SOLUTIONS USING BISMUTH(III) CHLORIDE

Corrosion inhibition effects of bismuth(III) chloride on iron in 1 N HClO4, 1 N HCl and 1 N H2SO4 were investigated by polarization measurements. The high inhibitor efficiencies obtained are attributed to the formation of a protective film on the iron surface. The persistence of the film was examined in an acid solution without inhibitors by impedance measurements. The film is more persistent than the films formed from tri-ethylstibine and tri-ethylbismuthine which have been examined previously. The homogeneity in appearance and uniform distributions of the elements, Fe and Bi on the iron surface were confirmed by EPMA. X-Ray photo-electron spectra showed that the protective film consists of two layers. an outer layer composed of ferrous and bismuthous oxides and an inner layer of metallic bismuth. The high efficiency of the inhibitor is mainly ascribed to the outer layer and the marked persistence of the film to the inner layer.